<script>
  var xhr = new XMLHttpRequest();
  xhr.onreadystatechange = function () {
    if (xhr.readyState === XMLHttpRequest.DONE) {
      if (xhr.status < 200 || xhr.status >= 300 && xhr.status !== 304) {
        alert('服务器异常');
        return;
      }
      console.log(xhr.responseText);
    }
  };
  xhr.open('GET', 'hello.php');
  xhr.send();
</script>
<a href="../首页/page10.html">
  <h2>返回上一页面</h2>
</a>